1.
Moment arm is a useful concept for these problems. Draw a line from the pivot point to the
closest point on the line of force. This is r*sin(theta) from the equation for the magnitude of
torque.
B6 ROTATION NOTE: Moment arm is a useful concept for these problems. Draw a line from
the pivot point to the closest p on the line of force. This is r'sine from the equation for the
magnitude of torque. See Ch 12 for details B6 QRT07: THREE EQUAL FORCES APPLIED
TO A RECTANGLE-NET TORQUE DIRECTION Three forces of equal magnitude are applied
to n 3-nmt by 2-m rectangle. Forces and act at 45° angles to the vertical as shown, while , acts
horizontally. (a) Is the net torque about point A ) clockwise, (il) counterclockwise, or (iii) zervo?
Explain your reasoning 45 45 (b) Is the net torque about point B (G) clockwise, (ii)
counterclockwise, or (ii) zero? Explain your reasoning (c) Is the net torque about point C (i)
clockwise, (ii) counterclockwise, or (ii) zero? Explain how you determined your answer
Copyright 2015 Pearson Education, Inc. 207
Solution
a)CLOCKWISE
because F2 has no contribution to the net torque. F1 produces a clockwise torque at A
b)Zero
Because, F3 has no cobntrinution to net torque at B, F1 and F2 creates equal and apposite
torques about B and gets cancelled, hence zero torque at B
c)Zero
Because all forces goes through C and hence distance is zero so the torque is also zero.